Stockholm, Sweden — Swedish company X-Force debuted in the United States its line of fitness equipment designed for negative-accentuated training at IHRSA 2009 last month in San Francisco. The strength training machines feature a weight stack that tilts to 45 degrees when an individual initiates a positive stroke. When the exerciser shifts to a negative movement, the weight stack automatically tilts back to the vertical. The company said this negative-accentuated approach creates greater muscle stimulation for added strength, since the weight load increases in the negative phase.